The present invention relates to an improved mattress for sleeping or the like.
In prior art mattress constructions, the resilient layer is almost exclusively formed of foamed plastic or foam rubber, spiral springs or combinations of the same, spiral springs that form a suspended face, or separate constructions formed by bags of water/air. It is a common feature of all of the resilient layers mentioned above that each of them are elastic at locations in the directions of the loads only. With the exception of the water or air mattresses, such prior art mattresses are hardly able to transfer the support of the load to other points in the transverse direction in the mattress. Thus, the support face becomes small, so that, as a result, high support forces and, thereby, high surface pressures are applied to the parts of the body lying on the mattress.
German Patent Application No. DE 1,940,763 describes a mattress construction which consists of a number of separate layers. In order to adjust the hardness of the mattress, it is possible to place a board that is made of a material that resists bending, such as wood, plastic, or plywood, between the layers. The dimensions of the board preferably correspond to the surface dimensions of the mattress. In practice, such a rigid board transfers forces in the mattress in a vertical direction only.
Denmark Patent Application No. DK 146,752 describes a mattress construction in which grooves are formed in inner foamed-plastic halves of the mattress. The grooved foamed-plastic layers are placed against each other so that the grooves are placed facing each other. The faces of the foamed-plastic halves have been fixed to each other by gluing them by means of an inelastic non-woven fabric. This construction transfers forces practically in a vertical direction only.
Finnish Patent No. FI 73,359 describes a mattress in which two surface layers of foamed plastics of different hardness grades have been joined together by means of a middle layer. The middle layer comprises sets of air ducts. When the mattress is turned around, two mattresses of different hardnesses are obtained. The middle layer equalizes the surface load over a wider area in the lower surface layer in the vertical direction.
Finnish Patent No. FI 49,108 describes a mattress in which a rigid, non-deformable board is placed inside an upper foamed-plastic layer. By means of the board, the surface forms of both of the mattress parts are affected.
In addition, Finnish Patent Application No. FI 843092 describes a mattress construction comprising a first and a second resilient support face, each of which is fixed to a rigidifying board that constitutes the middle part. The rigidifying board is composed of a number of pivotal parts in order to permit the rigidifying board to be deflected in one direction only. The pivotal parts also permit deflecting of the whole unit or rolling of the unit into a roll for storage.
A significant drawback of all of the mattress constructions mentioned above is the unequal surface pressure present in the mattress construction and the mere presence of vertical resilience without equalization of pressure in the horizontal direction. A further drawback of the prior art mattress constructions is the high and indefinite height of resilience. Moreover, the mattresses described in the above-mentioned references do not give the body a stabilizing support, which would reduce the surface pressures applied to the person.